With the increase in requirement for miniaturization of semiconductor devices, fine processing technology involving patterning a resist (curable composition for photoimprint) on a substrate (wafer) with a mold to form a resist pattern on the substrate has been attracting attentions, in addition to known photolithography technology. The fine processing technology is also called photo-imprint technology and can form a fine structure of the order of several nanometers on a substrate. In the method using a photo-imprint apparatus, a resist is applied to a pattern-forming region on a substrate and is then patterned using a mold provided with a pattern. The resist is cured by irradiation with light and is then released. Thus, a resin pattern (photocured product) is formed on a substrate.
In the formation of a resin pattern (photocured product), it is desirable to uniformize the residual film thickness of the resin pattern (photocured product) on a substrate. For example, in production of a semiconductor device, such uniformization can prevent occurrence of an in-plane variation in line width when a dry etching is performed, for example, in an etching step, i.e., in a step other than the pattern-forming step with an imprint apparatus. PTL 1 discloses a method of uniformizing the residual film thickness of a resin pattern (photocured product) through an imprint process involving optimization of the arrangement of droplets of a resist depending on the density of the pattern for transfer when the resist is applied onto a substrate by an ink jet system. In this imprint process discretely arranging a resist on a substrate, however, since the resist hardly spreads on the substrate, air bubbles readily remain between the resist and the pattern portion of a mold pressed against the resist on the substrate. The cured resist with remaining the air bubbles has a risk of forming a resin pattern (photocured product) having an unintended shape. Alternatively, if the curing is not performed until disappearance of the air bubbles, the productivity decreases.
PTL 2 discloses a method of promoting disappearance of remaining air bubbles by introducing a condensable gas between the mold and the substrate. The condensable gas condenses by the capillary pressure generated when a resist penetrates into a gap between the resist and the mold or into a concave on the mold. Accordingly, the supplied gas condenses by the application of the resist to reduce the volume, resulting in promotion disappearance of the air bubbles. The condensable gas used in the method described in PTL 2 is trichlorofluoromethane (CFCl3). In addition, NPL 1 describes an improvement in the property of filling by using 1,1,1,3,3-pentafluoropropane (CHF2CH2CF3) as a condensable gas.